feat(settings): add first-run confirmation dialogs for proxy and usage features

Prevent accidental activation of advanced features by showing a one-time
info dialog. Once confirmed, the flag is persisted in settings.json and
the dialog never appears again.

- Proxy: confirmation when toggling proxy server ON for the first time
- Usage: confirmation when enabling usage query inside UsageScriptModal
- Enhanced ConfirmDialog with "info" variant (blue icon + default button)
- Added i18n translations for zh, en, ja

src/types.ts

@@ -214,6 +214,10 @@ export interface Settings {
   silentStartup?: boolean;
   // 是否启用主页面本地代理功能（默认关闭）
   enableLocalProxy?: boolean;
+  // User has confirmed the local proxy first-run notice
+  proxyConfirmed?: boolean;
+  // User has confirmed the usage query first-run notice
+  usageConfirmed?: boolean;
   // 首选语言（可选，默认中文）
   language?: "en" | "zh" | "ja";